Bentley's says that at some point (it doesn't say when) Volvo started putting the pressure damper at the fuel pump inlet hose in response to complaints about fuel pump noise. In context it seems that they are referring to general noise making it into the car, not the extra noise caused by, say, a bad transfer pump.

When did they start putting the fuel dampers in, and how exactly does the damper result in less noise transmitted into the car?

For those of us who welcome any opportunity to quiet down the rather noisy 240 interior, is the difference noticeable enough to consider retrofitting a fuel damper if we don't have one?